Another Dataset question

[Robert Bravery]

Hi All,
I'm New to VS.net. Trying to figure out this new dataset thingy.
Ok so I add a dataadapter with all the correct properties for a table. Then
generate the dataset. Now open the dataset and drag another table from the
server explorer, set up some relations there. Set up two grids, one a s a
parent one as a chgild. Fill the dataset, run the form
But my child grid never gets any records.

I then added another datadapter for the child tabel, regenerated the
dataset, resetup the relatiosn. Now it works

Do I have to have a datadapter for each table that I am working with. If
this is so, why allow the user to drag and drop a table onto the dataset.

Covert your answers

Thanks
Robert

 

[Bart Mermuys]

Hi,

Hi All,
I'm New to VS.net. Trying to figure out this new dataset thingy.
Ok so I add a dataadapter with all the correct properties for a table.
Then
generate the dataset. Now open the dataset and drag another table from the
server explorer, set up some relations there. Set up two grids, one a s a
parent one as a chgild. Fill the dataset, run the form
But my child grid never gets any records.

I then added another datadapter for the child tabel, regenerated the
dataset, resetup the relatiosn. Now it works

Do I have to have a datadapter for each table that I am working with.

Yes. That is if you want to store to and load from a DB.

If this is so, why allow the user to drag and drop a table onto the
dataset.

There is a difference between a typed DataTable and a DataAdapter. A typed
DataTable is 'configured' inside a DataSet schema, from there code is
generated for the typed DataSet class and the typed DataTable classes, then
the typed DataSet/DataTable's can be instantiated from code or with the
Designer.

A DataAdapter on the other hand is just a class like any other, it can't be
configured inside a DataSet schema, it can only be instantiated and
configured at runtime from code or from designer.

Hence dragging a Table from Server Explorer into a Typed DataSet, doesn't
create a DataAdapter, where would it need to create one ? on Form1, on
Form2, in some code file ? No you need to create your own DataAdapter
where you need it, you could create it with the Designer on a Form or within
code (if you need the same on different forms).

In 1.1 the DataAdapter (on a Form) can however be used to generate a typed
DataSet. The simpliest steps for a master-child are to drag the two tables
from Server Explorer onto the Form, this should create two DataAdapters,
then right-click on the Form and choose "Generate DataSet", make sure both
tables are checked and click ok. Then you could open the typed dataset in
schema designer to check if there is a relation (and add one if there
isn't).

All this is one of the important changes in Net2.0, in Net2.0 there are
TableAdapters, they are similar to DataAdapters except that now they are
generated classes that are also configured inside the DataSet schema, just
like typed DataTable's.


HTH,
Greetings

 

[Robert Bravery]

Hi Bart,
thanks for the explanation.
So if I understand correctly. The same datasetcan be used on many different
forms as long as there are the correct dataadapters on each form. Is this
correct

Thanks
Robert

 

[Bart Mermuys]

Hi,

Hi Bart,
thanks for the explanation.
So if I understand correctly. The same datasetcan be used on many
different
forms as long as there are the correct dataadapters on each form. Is this
correct

To be more precise each Form can have an instance of the same typed DataSet,
yes. Keep in mind that each Form will have its own instance, so the data
isn't shared between Forms this way. You can create as many instances of
the typed DataSet as you want (whether this is in code or on Forms) .

And yes, you'll need to have a correct DataAdapter on each Form. So if you
have multiple Form's that need the same DataAdapter then you could consider
doing the DataAdapter configuration from a code file, class or module and
then use that instead of placing the same DataAdapter on multiple Forms.


Greetings,
HTH

 

[Robert Bravery]

HI,
Ok now that makes more sense. I would have to learn how to do this tho.
Moving from one language to another is rather difficult.

Robert